There are a number of surgical techniques for treating clouding within the eye lens, which is referred to as a cataract in medicine. The most common technique is phacoemulsification, in which a thin needle is introduced into the eye lens and excited to vibrate via ultrasound. The vibrating needle emulsifies the lens in its direct vicinity in such a way that the created lens particles can be suctioned away through an aspiration line via a pump. In the process, a rinsing fluid (irrigation fluid) is supplied, with the particles and the fluid being suctioned away through the aspiration line, which is usually arranged within the needle. Once the lens has been completely emulsified and removed, a new artificial lens can be inserted into the empty capsular bag, and so a patient treated thus can regain good visual acuity.
During the emulsification of the eye lens via ultrasound, the vibrating needle and a sleeve surrounding the needle rub at the tissue of the eye to be treated, and so there can be strong heating of the contact region. In the case of relatively long operation of the vibrating needle, the tissue region around the needle can burn. Since the needle is punched through the cornea, this means that the cornea in particular is subject to a very large thermal load. Even an only locally burnt cornea is classified as a grave complication, which must be avoided at all costs.
United States patent application publication 2013/0237900 discloses a control device for an ophthalmic surgical system, which has a measuring device for establishing the volume of an anterior chamber of the eye of an eye to be treated during a phacoemulsification and a control unit which calculates a controlled variable as a function of the established volume of the anterior chamber of the eye. A pressure or a volume flow in an irrigation line and/or aspiration line of the ophthalmic surgical system can be controlled via the controlled variable.
United States patent application publication 2011/0218483 A1 discloses a phacoemulsification handpiece which has a needle and, coupled thereon, a microelectromechanical system (MEMS). Furthermore, the handpiece can have a horn, wherein the horn is coupled to the needle and the MEMS. The MEMS is configured in such a way that it can generate a movement of the needle in at least one direction.
United States patent application publication 2010/0094321 A1 discloses an ultrasound handpiece for the phacoemulsification, which has at least one pair of vibrating piezo-elements that are arranged within the handpiece in such a way that they generate vibrations which are oriented perpendicular, or inclined at an angle, to the longitudinal axis of the handpiece.